Physiognomy and Structure: No Data Available

Floristics: Vegetation is characterized by light-demanding, tough-rooted herbaceous perennials tolerant of frequent inundation and flood-scouring. Carex torta is usually the dominant species and typically forms dense, extensive colonies. Associated species vary with geography. Polygonum sagittatum, Solidago rugosa, and Dichanthelium clandestinum are typical; others include Acalypha rhomboidea, Amphicarpaea bracteata, Boehmeria cylindrica, Equisetum arvense, Eutrochium fistulosum (= Eupatorium fistulosum), Euthamia graminifolia var. graminifolia, Juncus effusus, Hypericum mutilum, Hypericum perforatum, Impatiens capensis, Leersia oryzoides, Lobelia cardinalis, Lycopus virginicus, Onoclea sensibilis, Osmunda regalis, Prunella vulgaris, Solidago patula, Symphyotrichum dumosum (= Aster dumosus), Symphyotrichum lateriflorum (= Aster lateriflorus), Symphyotrichum prenanthoides, Thalictrum spp., Trautvetteria caroliniensis var. caroliniensis, Verbesina alternifolia, and Vernonia noveboracensis. Cover by nonvascular plants is insignificant. Physiognomy of this type varies from strictly herbaceous to wooded herbaceous to shrubby. Scattered shrubs and small, battered specimens of Platanus occidentalis, Betula nigra, Cornus amomum, Alnus serrulata, and Carpinus caroliniana are present in some stands. An overhanging canopy with an average cover of 20% may include Platanus occidentalis, Betula alleghaniensis var. alleghaniensis, or Acer rubrum. Sparse overhanging shrubs often include Rhododendron maximum. Stands in disturbed landscapes may be heavily invaded by Microstegium vimineum, Polygonum cespitosum var. longisetum, and other weedy exotics. Mean species richness of vascular plants in six West Virginia plots was 36 taxa per 400 m2, with most of the diversity in the herbaceous stratum.

Dynamics:  Periodic large or severe floods transport and deposit large numbers of cobbles, stones, and even boulders in characteristic bars both within the channel (islands) and along its edges (streambanks). These bars provide a matrix for deposition of finer alluvium and habitats for the establishment of tough, adaptable herbaceous plants, which in turn stabilize the bars with massive networks of perennial rootstocks. Regular flood-scouring batters or removes woody plants which take root in these habitats, maintaining open-canopy conditions. These habitats are highly dynamic, with conditions more or less constantly shifting in response to an irregular but powerful disturbance regime. While some of the bar habitats may be damaged or removed by severe floods, others may accrete or be newly deposited during the same events (Hupp 1982). Successionally, this unit can be considered a pioneering type on new, coarse alluvial land, but it is also more or less permanently maintained by natural disturbances.